package map;

public class LinkedListMap<K,V> implements Map<K,V>{

    private class Node{
        public K key;
        public V value;
        public Node next;

        public Node(K key, V value, Node next){
            this.key = key;
            this.value = value;
            this.next = next;
        }

        public Node(K key){
            this.key = key;
            this.value = null;
            this.next = null;
        }

        public Node(){
            this(null,null,null);
        }

        @Override
        public String toString() {
            return key.toString() + ":" + value.toString();
        }

    }

    private Node dummyHead;
    private int size;

    public LinkedListMap(){
        dummyHead = new Node();
        size = 0;
    }

    public void add(K key, V value) {
        Node node = getNode(key);
        if(node == null){
            dummyHead.next = new Node(key,value,dummyHead.next);
            size ++ ;
        }else{
            node.value = value;
        }

    }

    public V remove(K key) {
        Node prev = dummyHead;
        while(prev.next != null){
            if(prev.next.key.equals(key)){
                break;
            }
            prev = prev.next;
        }

        if(prev.next != null){
            Node delNode= prev.next;
            prev.next = delNode.next;
            delNode.next = null;
            size--;
            return delNode.value;
        }

        return null;

    }

    public boolean contains(K key) {
        return getNode(key) != null;
    }

    public V get(K key) {
        Node node = getNode(key);
        return node == null ? null:node.value;
    }

    public void set(K key, V newValue) {
        Node node = getNode(key);
        if(node == null){
            throw new IllegalArgumentException(key + "不存在");
        }
        node.value = newValue;
    }

    public int getSize() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    private Node getNode(K key){
        Node cur = dummyHead.next;
        while (cur != null){
            if(cur.key.equals(key)){
                return cur;
            }
            cur = cur.next;
        }
        return null;
    }
}
